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June 18, 1935. LE ROY J. LEISHMAN TELEVISION APPARATUS AND METHOD,

Filed Jan 27, 1931 Patented June 18, 1935 omrEo STATES PATENT, OFFICE I14 Claims.

This invention relates to improvements in television apparatus and,specifically, to framing the received image to accord with thedesiredrelative position between the transmitted imagein space and theframe in, or on; which said image may appear.

The objects of this invention are to frame the received image so thatits outlinescoincide with the outlines and boundaries of the receptionframe, or to produce any desired relationship between the area of thetransmitted image and that of the area 'wherethrough, or upon which, itmay be received, which may be the exact centering of the image with thereceiving name, or its relative distortion ifthe latter be desired; I

Other objects willappear as this description proceeds. r 1

While applicable to, any present known method of transmitting picturesor images, the, principle is most simply illustrated by adescription ofits application to the, well-known scanning disc system of television.

In the drawing: I Figs; 1 and 2 show diagrammatically, the elements of atelevision sending and receiving scanning arrangement in whichperforated discs are employed, Fig. 1 being the sending disc and Fig. 2the receiving disc. 3 I

Fig. 3 shows a front elevation of aframe or receiving area cooperatingwith a special form of reception scanning; disc,.said frame beingprovided with the adjusting features of this invention, one,positionbeing shown in full lines, another position being shown in,dotted lines.

Fig.4 is a side elevation of same, partly in section, one positionbeingshown in'iull lines and another position being shown in the dottedlines.-

In the figures, A, B, C and fD are the boundaries of the receiving areaor frame of the receptor, while a, b, c and d are the correspondingcorners of the sending frame at the originating station. necting wires.It is herein assumed, for simplicity, that the sending andreceivinginstruments are electrically connected by wires, although, itis obvious that electric waves sent out from a station through thespace, or the luminiferous ether, between station and receivingapparatus will produce a ,similar' effect, if sufficiently strong, tovary the brillance of a light controlled by? aphoto-electric cell.

H is a scanning disc, ,K. an axle to which the discis attached androtated by anyfsuitable means, as motor M. L? is a source of illumi- HO.a d e nation energized electrically and which varies in brilliance withvariation in current flow through it. I The use of photo-electriccellsfor varying the flow of current through any suitable. electricaldevice, responsive to changes in the intensity of light to which theyare subjected, is well known and not a part of this invention;therefore'is merely mentioned to make clear the operation of thescanning. discs and the movable frame. i

The usual scanning disc, shown in Figs. 1 and 2, comprising a thin,circular disc H provided with small holes I, 2, '3, etc., to the' lasthole, here numbered 20. These. holes are arranged in spiralrelationship, the first, I" having a radial distance from the centre ofrotation of the disc equalto K-l b or K-2 B, while the last hole, 29,has a radius equal to KI d or K'.2D, the distance of each hole from thecentre increasing from K D to K B progressively and equally byonetwentieth this distance. apart of the holes is constant and "equal tothe totalcircumference. divided by the numberof holes, which, for thisparticular case,-wou1d"be- 18 degrees apart. 'The scanning disc ll-2rotates behind'a thin opaque sheet, J'2 preferably of rigid" material,having an opening, or window, Z,

through it, which, in the case of a rotatingdisc,

window A, B, C and D, there being one spot or ray of light from lamp Lthrough a hole in disc H falling on, or visible through, the window areaat each instant, which light corresponds imposition. in the receivedpicture with the position of thehole through the scanning disc, anditsrelation to the image being transmitted, at the transmitting station.By

The angular distance running thedisc at aspeed which makes a Irevolution in about of a second, all of the holes successively pass overthe window opening within that time. Hole I passes across the windowfrom right to left, following the upper edge of the window as indicatedby the suc-;

cession of dotted holes. As hole I passes from the opening A, B, C andD,,, at theleft edge, hole 2 enters at the right edge at a slightly lessradius, traverses the width of the window at that radius, passes behind,and is obscured by the sheet in which the window Z is out. Then hole 3follows, and so, successively, do the others, the angular spacing of theholes being constant as indicated, and equal to the angle subtended bythe window A, B, C and D. By following the paths of the holes, it willbev seen that the entire number covers the total area of the window,each one passing entirely across it at one radius, the next followingacross it at a radius which is less than that of the preceding hole by adistance equal to the diameter of the holes, so that the radius of theinner element of one is identical with that of the outer element of thenextsucceeding one. Thus the twenty holes scan and cover the entire areaof the window, and admit light to illumine this area in varying degreesof brilliance; Of course, in-practice, the number of holes exceedstwenty, being usually forty-eight or fifty.

It is obvious that only one hole can appear over the open space at anygiven instant and the I .clearness of definition depends on the numberof holes which pass over the window opening within any given time.

If an image be east through frame a, b c d of sending disc H-l Fig. 1,the reflected light of each point, or tiny area, of the image will passthrough one of the holes of disc. Since the movement of each hole coversa horizontal strip of the received picture, and the successive stripstravel radially from top to bottom of the frame "a, b, c, d, it isobviousthat if light reflected from the unitary elements of the imagepasses through the holes in sending disc HI and impinge on a photo.-electric cell, diagrammatically indicated at Q, the current flow fromsource T through cell Q over wires and P and through lamp L will varywith the degree of brilliance of the spot of light passing througha'hole in the disc H.l. Hence, the spot of light from lamp L passingthrough'a hole in disc H-2 at the same instant will have a brilliancy toaccord with that passing through sending disc H-i. If disc H -2 besimilar to disc H--l and they are rotated at identical speeds, each spotof light through disc H-l" is exactly reproduced by the spot throughH-2, since each tiny area of the image reflects a certain amount oflight and these small areas swiftly and successively cover the entirearea of the image, the exact reproduction of the image light, and shade,on unitary, areas at the receiving disc, will reproduce the image. Butif the position of the holes in the two discs are not identical, theimage will not be centred in the receiving frame. For instance, if hole2 of the sending disc H-I is passing in front of the image while hole [6of receiving disc H2 is passing over the frame, the part of the imageseen through hole 2 is shown in the position of hole I 6. in thereceiving area, so that the top of the image begins to show near thebottom of the frame.

Also, if hole 2 in the sending disc begins to enter the sending field atthe left edge at the instant when hole l6 has moved half the receivingwindow, or frame, and only half of the image will be seen from right toleft,

' the other half showing from the left edge to the middle of thereceiving frame. Therefore, for the image to be received in the sameposition as that of the transmitted image each spot of light throughdisc H--2 must fall on a position corresponding with the position onwhich the light beam through H-l" falls at the same instant. For thiscondition, it is essential that discs H-l and H2 not only be rotated atidentical speeds, but the instantaneous positions of the two discs mustbe identical.

Various expedients have been tried to frame the transmitted image sothat it will be properly centred in the frame, this inventionconstituting a novel and simple means for this purpose.

As shown, in Fig. 3, the reception scanning disc has the series of holesextended to form two complete spiral turns around axis K instead of asingle spiral turn. This permits two spots of light to passsimultaneously through the disc. One of the spots is obscured by anopaque movable interceptor F, in which an opening "A, B, C, D is formedof the size and configuration for the picture. Member F is adapted to beturned through a small angle about K and to be moved radially asindicated by the dotted lines, Fig. 3.

The receiving disc H, having holes around two complete spiral turns, twopictures could be simultaneously received if disc H were synchronized inposition with the sending disc and two receiving areas or frames wereprovided, one receiving the picture in the radial zone extending fromhole I to hole the second being received in the zone from hole 2| tohole 40. Obviously, by having a receiving frame" of the size of a singlepicture and moving it relatively to the disc-holes or light rays, thereceived picture can be caught in any position in the frame.

As shown in Figs. 3" and 4, disc H, driven by motor M, is supported byflat vertical member J, through which an opening, Z, is formed, longenough to cover the radial extent of the double spiral and considerablywider than the reception surface. In front of the disc H is placed fiatradial member G adapted to move angularly about axis K and having a holeX therethrough substantially as long as the hole Z and subtending anangle equal to that of the hole spacing. Member G may be turnedangularly to any position and locked there by any desired means, such asproviding considerable frictional resistance to motion and movingmanually. However, for ease in manipulation and accuracy of positioning,the worm E mounted on supporting member J and mating sector N attachedto member G are provided where-by angular motion may be imparted tomember G.

Lying flat against member G is member F arranged for radial movement andthrough which is formed the sector shaped opening A, B, C, D,constituting the picture-receiving window" or frame.

As one practical means for moving member F radially and looking it inany position, the screw R, mounted on member G, and cooperating nut S,fastened to member F, are used.

Clearly, the window or frame A, B, C, D, may be moved to receive lightrays from any series of holes through disc H beginning with any hole andending with the succeeding twentieth hole so that positioning the incomeit 'canremain fixed in position, but in order to concentrate the lightofa small lamp on the frame,it is fastened to the outer ,movablemember-Fby a screw W and angle member .fVias shown,,so that, the lamp will bemoved exactly;'with V the frame opening A, B, on, D.

, A brief summation of certain features of this invention in certain,aspects, includes the'provision of a scanning means which'directscradmits-light rays in a successive sequence to a. re-. ceiving area,on, or in, or through whichis a viewing framefor the reception orpassage of light rays which produce the image, the total number of therays to form a complete image being constant for any specific receptionapparatus; The scanning device is arrangedto direct two simultaneousrays of light of identical intensities on the receiving area, these twosimultane-' ous rays being separated at the receiving area by a distanceequal to the span of the viewing frame measured in the same. directionas that from ray to ray, which direction is substantially trans-, verseto the direction of movement of the scan-, ning means. Admission of twosimultaneous, spatially-separated light rays of identical in-, tensitieswhen only one instantaneous ray is'required for production ofv theimage, means that an excess of rayspass from the light-source.

Hence, some thereof must be obscured. ,Ihe obscuring of one ray opens apath for the other ray to fall on, or pass through, theimage-viewingzfram while if the second ray beobscured, thefirst ray willshow on or in, the viewing frame, but in a different position.Therefore, change in position of ,thescanning rays, or of theimage-viewing frame, will obscure certain rays and permit passage'to orthrough the viewing frame of others, previously obscured. Since for eachray obscured, another, previously obsoured ray will be made visible, itis obvious that the, number of visible rays is always the same but theirpositions may be changed relatively to the viewing frame by relativechange in position between the rays and the frame.

The illustrative examples and embodiments herein of this invention'havedepicted the, scanning means interposed between the light source and theimage-viewingfiframe. But it is obvious thatother positionings of theparts is possible, and theyl may be assembled relatively in anyconvenient or preferred manner, the only essen-f tial conditions beingthat the total number of light rays which the scanning means is abletomove, or control, or transmibmust exceed the number used, or required,in forming the image, and that relative change in position between theviewing frame and the light rays; be' possible, which relative positionchange willobscure some of the said excess rays and permit otherspreviously obscured, to become visible or active, in-

forming an image. I i g In general, it isunderstood that many variantsof this invention are'possible, and, in its broader aspects, it is notlimited to any particular construction or application, as. changes in:the size, proportions, configurations, arrangements, as-

semblage, interaction, juxtapositioniand, mechanical relations, as wellas additions, omis-y. sions, substitutions, combinations and alterationsI offorms, parts, members and features maybe madewithcut departing'fromthe broad spirit of this invention. i H I 'olaim as my invention: r

1. In a television receiver, a scanning,-,disc having a plurality of"lightedirecting sections disposed inv a spiral having a plurality ofturns partially register with the viewing opening in said first member.1 e

2. In a television receiver, a scanning disc having a plurality oflight-directing sections disposed in a spiralhaving a pluralityof turns;

a flat opaque member pivotally mounted and substantially coaxial with,parallel to and adjacent said disc,the said member having a viewingopening therethrough, two of the sides,

whereof are substantiallyradial with the center of the scanningdisc,said member being adjustably rotatable about its said pivotalmounting, a second flat opaque member mounted on said first member,adapted to beadiustably moved radially of saiddisc and having aviewingopening therethrough adapted topartially register with theviewing opening in said first member, saidsecond opening having twosides substantially normal to a disc radius bisecting the saidfirstopem'ng. 3. Ina television receiver, a scanning disc having aplurality oflight-directing sections dis posed in a spiral having -,aplurality of turnspia fiat opaque member pivotally mounted andsubstantially co-axial with, parallel to and adjacent said disc, thesaid member having a viewing opening therethrough, two of the sideswhereof 1 aresubstantiallyradial with the center of the scanning disc,said member being adjustably rotatable about its said pivotal mounting,a second flat opaque member mounted on said first member adapted to beadjustably moved radially of said disc and having a viewing openingtherethrough adapted to partially register with the viewing-openinginsaid first member, said sec ond opening having two sides substantially'nor-,

mal to a disc radius bisecting the saidflrst opening; means for movingsaid first opaque member angularly, and a second independent means for'moving'lsaid second member radially, of the saiddisc. l v a 4, In atelevision receiver, the combination of a scanning dischaving a seriesof openings the locus whereof is a spiral having a plurality of turns; amember having a viewing opening therethrough, and pivotallymountedadjacent to and substantially parallel and co-axial with.

the scanning disc,sa id viewing opening having two sides radial ofsaidpivotalmounting, each side having-alengthsubstantially equal tojtwice Ithe-turn pitchof said spiral. I

5; In a television receiver, the combination of. a scanningdischaving, aseries, of openings the locus whereof .is a spiral having a plurality ofturns; a member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially co-axial with the scanning disc,said viewing opening having two sides radial of I said. pivotalmounting, each side having a length substantially equal to twice theradial distance between successive turns of said spiral, and means foradjustably moving said member angularly about said pivotal mounting.

6. In a television receiver, the combination of a scanning disc having aseries of openings the locus whereof is a spiral having a plurality ofturns; a member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially parallel and co-axial with thescanning disc, said viewing opening having two sidesr'adial of saidpivotal mounting, each side having a length exceeding the turn pitch ofsaid spiral, and means for adjustably moving said member angularly aboutsaid pivotalmounting; a second member having a viewing openingtherethrough mounted on said first-named member, two sides of saidlatter opening being substantially normal to a radius bisecting theopening through the first said member, the length of each of said twonormal sides being substantially equal to the distance apart ofsuccessive openings in the scanning disc at the radius of each of saidsides.

7. In a television receiver, the combination of a scanning disc having aseries of openings the locuswhereof is a spiral having a plurality ofturns; a member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially co-axial and parallel with thescanning disc, said viewing opening having 'two sides radial of saidpivotal mounting, each .side having a length exceeding the turn pitch ofsaid spiral, a second member having a viewing opening therethrough andmovably mounted on said first-named member, the opening in said secondmember having a radiallength substantially equal to the turn pitch ofthe said spiral; means for adjusting said first member angularly aboutits pivotal mounting and a sec-- 0nd means for adjusting said secondmember radially of thescanning disc.

8. In a television receiver, the combination of a scanning disc having aseries of openings the locus whereof is a spiral having a plurality ofturns; a member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially co-axial and parallel with thescanning disc, said viewing opening having two sides radial of saidpivotal mounting, each side having a length exceeding the turn pitch ofsaid spiral. V

9. In a television receiver, the combination of a scanning disc having aseries of openings the locus whereof is a spiral having a plurality ofturnsya member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially co-axial and parallel with thescanning disc, said viewing opening having two sides radial of saidpivotal mounting, each side having a length exceeding the turn pitch ofsaid spiral, and a second member having a viewing opening therethroughmovably mounted on said first-named member.

10. In a television receiver, the combination of a scanning disc havinga series of openings the locus whereof is a spiral having a plurality ofturns; a; member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially co-axial and parallel with thescanning disc, said viewing opening having two sides radial of saidpivotal mounting, each side having a length exceeding the turn pitch ofsaid spiral, and a second member having a viewing opening therethroughmovably mounted on said first-named member, two sides of said latteropening subtending an angle on the scanning disc substantially equal tothe angle subtended by successive openings in said disc.

11. In a television receiver, the combination of a scanning disc havinga series of openings the locus whereof is a spiral having a plurality ofturns; a member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially co-axial and parallel with thescanningdisc, said viewing openingh'aving two sides radial of saidpivotal mounting, each side having a length exceeding the turn pitch ofsaid spiral, and a second member having a viewing opening therethroughmovably mounted on said first-named member, two sides of said latteropening subtending an angle on the scanning disc substantially equal tothe angle subtended by successive openings in said disc, and a lightsource attached to said second member.

12. In a television receiver, the combination of a scanning disc havinga series of openings the locus whereof is a spiral having a plurality ofturns; a member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially co-axial and parallelwith thescanning disc, said viewing opening having two sides radial of saidpivotal mounting, each side having a length exceeding the turn pitch ofsaid spiral, and a second member having a viewing opening therethroughmovably mounted on said first-named member, two sides of said latteropening subtending an angle on the scanning disc substantially equal tothe angle subtended by successive openings in said disc; means foradjusting said first member angularly about its pivotal mounting and asecond means for adjusting said second member radially of the scanningdisc.

13. In a television receiver, the combination of a scanning disc havinga series of openings the locus whereof is a spiral having a plurality ofturns; a member having a viewing opening therethrough, and pivotallymounted adjacent to and substantially co-axial and parallel with thescanning disc, said viewing opening having two sides radial of saidpivotal mounting, each side having a length exceeding the turn pitch ofsaid spiral, and a second member having a, viewing opening therethroughmovably mounted on said first-named member, two sides of said latteropening subtending an angle on the scanning disc substantially equal tothe angle subtended by successive openings in said disc; means foradjusting said first member angularly about its pivotal mounting and asecond means for adjusting said second member radially of the scanningdisc, said two adjusting means being independently operable' 14. In atelevision receiver, the combination of a scanning disc, a source ofmodulated light, a movably mounted member having a viewing openingwhereof two sides are radial to the centre of said disc, a second member'movably mounted on said first member and having a viewing opening andindependent means for moving each of said'movable members.

